From Mods Repository Wiki
cod5\deffiles\xmodel.gdf in a hex/plain text editor. Delete the line near the bottom of the file which reads:
This will allow you to select any file as a physics preset, instead of having to get one from
cod5\share\main which doesn't exist.
cod5\deffiles\xmodel.dll in a hex editor, search for
and replace it with
This will stop the converter looking in main/physic/C:\blahblah\cod5, which is just messed up.
Convert your model in Asset Manager, oh and make sure you've given it a physics preset in
cod5\raw\xmodel, find the model you just converted and open it in a hex editor. Near the top you should see something like:
change that to this:
and there are always three characters before
raw\ which you need to select whilst editing it too. Those three chars are what you see when the original 'no physics preset' error comes up.
Now, compile your mod.ff and you're done!
You need to repeat Step 3 every time you re-convert the xmodel_export file in Asset Manager, but not every time you compile the mod fastfile.